1. Field of the Invention
The present invention relates to a current collector system structure to increase stability in current collection of a prismatic sealed secondary cell.
2. Background Art
In recent years, a cell-powered car using a secondary cell as a power source, such as an electric vehicle (EV) and a hybrid electric vehicle (HEV), has been becoming popular. However, a high power secondary cell is required for such a cell-powered vehicle. In addition, since sophistication of mobile electronic devices such as mobile phones and laptop computers is developing, higher output of cells is also required in these applications.
To obtain high output from a cell, it is necessary to increase a facing area between positive and negative electrodes of the cell. The facing area between the electrodes can be increased using a laminated electrode assembly in which a number of positive and negative electrode plates are laminated or a spiral electrode assembly in which long positive and negative electrode plates are wound via a separator. Therefore, these electrode assemblies tend to provide a high power battery.
The secondary cell using the laminate electrode assembly or the spiral electrode assembly adopts a configuration in which a current collector plate is welded to a core exposed portion where a core of the positive and negative electrodes is exposed, and this current collector plate is connected to an external output terminal. In the high-power battery, it is important to stably take out high current. For the purpose of taking out a stable high current, it is advantageous to extend a contact area between the current collector plate and the positive and negative electrode cores to increase welded points. Thus, it is carried out to use a current collector plate wider than ever before in order to increase welded points between the current collector plate and the positive and negative electrode cores.
However, in a laminate-type high capacity secondary cell having a large number of windings or layers, it is not easy to extend a contact area between the current collector plate and the positive and negative electrode cores relative to the gross area of the electrode plates. Even if a wide current collector plate is used, high current cannot be taken out.
Regarding techniques for reducing the electrical resistance in the current collector system, a variety of current collecting structures have ever been proposed. For example, techniques in the following patent documents 1 to 4 are proposed.